Profile method of making steel



Aug. 18, 1953 J. F. JORDAN PROFILE METHOD OF MAKING STEEL INVENTORF Filed Nov. 2, 1951 Patented Aug. 18, 195 3 UNI PATENT OFFICE .Park, Galif.

Application Noveniben 2, 1951, SerialNo. 254,513

'My invention relates .towmcl a k li y wherein molten iron containing canbon; -is -bessemepiaed to yield a' low-carbon: iron.

This is a continuationr inepartohmyapplication, Serial No.:745,'853'..of-1May 3;.1947, now abandoned, the continuatiomimpa-rt, fier-ial 510. 29,029 of May 25, 19::8;nowgabandoned thepon tinuation-in-part, Serial :=NO'. v .lf52;.650. =of lvlarch 29, 1950, now abandoned;and -mycopending.continuation-impart, Serial; No.2 1168-39-1 10f June 14', 1950, now abandoned.

The principal objectivesofi my; invention is to provide the continuous;bessemer-prooflss ,,Wit a method of control ;7 the lach of .asmebhfid of control being a principal: reason ,why. s -teel metallurgists havenever seriouslyaundertaken to;manufacture steel continuously. rotherlob-jeots'will be apparent in my specification;and claims;

The expression airf is employedrto denote; air, oxygen gas, concentrated-oxygen:gas;-or-; air enriched with oxygen gas;

In a continuous besse'merzprocess, =the, 1nolten' metal is confined to .fiow aszastreamvalonga refractory trough. as aseriesl of ainijets impinge into the flowing metal stream, sai'dgseries of i mpinging j s ing spreadout-sui oiontlvalone said stream to resolve the refining.-reactionsf-into a series ofrefining zonesewhich-gradually blend into each. other, each; ofa.saidqrefininglzones.be

ing characterized hyithesllbslianti ally similar free energy of the reactipnsatalging place2 therein. in general, the silicone and 1minganilseirare oxidized in the first of'these zonesa-togetherlwith a certain amount of=carbonrfiThis firstzQneradut lly blends into a second- Zzqna, wherein 1 t etlo lan of the carbon is oxidized: rfjf the process is being v carried out under axbasicssla and und rzoon tions wherein the iron oxide QQHEGIIEOfzSfi-ldgbfifih) slag is maintained ,at a relatively;- iglnlevel; the phosphorus and s h r oontonti fiit o flowin metal stream will pass'intothe basic slag stream as said metal stream flows thruzonesone and two, so that, by the timethat decarburizationis essentially complete, the removal Oi -the: silicon;- manganese,phosphorus andsulphur:isessentially complete also. If, on,the gtherhand -theiron oxide content ofithe basimslagistream is. not maintained at a relatively high leyel saidadecarburizing' zone maybe followed-lbya.:third-: zone wherein dephosphoriza-tion i'sachieved as the Jimpinging air j ets-raisethe oxygen-level in the essentially-decarburized" ironi In the event that the metal stream is flowingin contact with -an acid" slag stream; the refining 'process? is-d-iVidBd into the mentionedzones orle andtwo; deph'os- 2 phorization and desulphurization not being a part ofthe process. 4

Two methods of regulating this process are available: (1); by regulating the oxygen input into the flowing metal stream, and (2) by regulating the input of the raw iron into the process. Of these thefiormer is preferable. The input of oxygen into the flowing metal stream may be regulated by regulating the amount of oxygen being introduced by means Iof the impinging air jets, or by regulating the input of iron oxide into the flowing metal stream, or by regulating the iron oxide content of the molten slag stream incontact withwhich said metal stream is flowing, or by regulating several of these regulatin means in combination. Of these,'. the simplest procedure is to; form said air jets by means of orifices which are all connected toa common manifold, and then, by regulatingthe air pressure within said manifold, regulating the amount 10f oxygen'beingintroduced into the metalstream. I-Iowever, whichever method of regulating. the process is to be used, it isfirst necessary to know just how the process is progressing;

"Ihe-figureshows a refining trough in which my method otpontrol is mounted. Trough l! is formed by refractory body. 56. Incoming raw metal ,IB flovvs into trough .IT to form flowing metalstream M, and stream i4 is refined asiit' flows-along trough H by means of a series .of impinging air jets which enter trough ll thru ports H, the refinement proceeding as said air jets impingezinto contact with slag stream i2 and .metalstreaxn l l, the plane of contact between streams l6 and 52 being referred to as slag metal interface I 3..

I controlthe' composition of the metal product by controlling the location of the flame profile that-appears above datum line lll datum line H] being atonee the top oftrough i1 and the visiblebase of the flame profile appearing thereabove, asseen tby an observer positioned to one sidepf troughll, as in the figure. The flame profile appearing above any given position along the decarburizin'gphase of the process bears a simple andgdir ec't relationship to the progress .0f the reactionstahing-place therein and thereunder, forsaid fiamegprofile arises from said reactions.

c r n y lzs road. the flam o l alo stream 14 :within trough I! so that i may seea substantially continuous picture of the progress of ,the reactions which are taking place therealon @W th-the r a o s s re do -sumoioot y to, resolve the flame- ;profile into discernible features ;wh,io .:p otu ;.t pr r ss; f. p o e sented as A. As stream [4 flows along trough H;

the silicon and manganese are oxidized, together with a certain amount of carbon-the progress of these reactions being represented by a flame profile that may assume the general shape shown between A and B. As the flow proceeds, and the temperature of stream Hi mounts, the height of the flame profile gradually mounts alsodue, in

the main, to an intensification of the decarburizing reaction. The progress of this intensification is shown by the flame profile and'may take the general form shown between B and CC representing the decarburizing reaction at the height of its intensity. As C is passed, the profile of flame falls into a rapid decline or break, represented between C and E. D represents an arrest that sometimes occurs in break CE, particularly in an acid practice, being presumably the result of the sudden oxidation of some compound or element that yields a flame of high luminosity. Following arrest D, or in the absence of arrest D, the profile of flame continues to decline until E is reached. E represents the process end point or terminal point, insofar as the oxidation of carbon is concerned, and, as mentioned previously, E may be caused to represent the point whereat the eliminationof carbon, silicon, manganese, phosphorus and sulphur is completethat is, to the degree contemplated by the process.

The profile of flame arising from a continuous bessemer process may be resolved into the required discernible'features by any method that will spread out the reactions along the metal stream within the refining trough. Thus, the profile may be spread out by increasing the distance between ports H, and thereby increas ng the length of said profile and the refining area by delaying the progress of the reactions, or said profile may be spread out by decreasing theinput of air thru said ports H and then increasing the number of ports H at one, or both, ends of the refining area, thus lengthening the refining area and delaying the progress of the reactions.

It is essential to the success of my control process that incoming raw iron 18 be uniform with respect to temperature, chemical composition, and its rate of input into stream Hi. This is not to say that changes cannot be tolerated, but only that such changes must be made gradually; for, the flame profile cannot be satisfactorily employed to control the process if sudden changes in temperature, chemical composition, and/or rate of raw metal input are being continually encountered. This uniformity requirement does not offer any serious handicap to my control process, for this uniformity problem has long since been solved in conventional steel plants by means of the hot-metal mixer. The rate of flow of raw iron is into stream I4 may be regulated in a number of ways. Thus, for example, the hotmetalmixer may be equipped with a replaceable carbon orifice that is submerged below the surface of the molten metal contained therein, and

4 then, with the molten metal passing thru a weighing device as it emerges from said orifice and flows into stream [4, the rate of input into said stream It may be regulated by regulating the depth of immersion of said orifice. This method of regulating the rate of input of raw iron 18 into stream l4 was disclosed and claimed in my copending application, Serial No. 213,718 of March 3, 1951, now abandoned.

Whether the continuous besserner process is operating under a basic or an acid slag, the procedure for placing my control method into op- .eration may be, substantially as follows: with stream [4 flowing along trough I! at a uniform ratethe temperature and chemical composition of incoming raw iron l8 being uniform, the impinging airjets are brought to bear on the flowing metal stream, causing the erection of a proflle of flame above datum line H]. The input of oxygen into stream [4' is increased until the metal that has passed'the last impinging air jet conforms in composition to-the desired productv presumably, but not necessarily, an iron containing about 0.05% carbon. With the process pro- 3 ducing the desired product, the flame profile is examined for the flame feature that is to be em-- ployed for control purposes. In general, the flame feature should be selected from that portion of the profile of flame lying between C and the point along stream l4 whereat the profile of flame disappears below datum line it. The nearer the selected flame feature is to the point whereat the profile disappears below datum line E0, the more accurate and responsive will be the controlling action. An arrest, D, may be the selected feature, or the point whereat the profile disappears below datum line I0 may be selected as a suitable feature, or the height of the flame profile at a selected position in the C-E break may be chosen asa suitable feature; In any case, with the process producing the desired product, the position of the selected flame feature along stream M within trough H is noted. With the location of the selected feature noted, the 0011-:

tinued production of thedesired product is assured so long as said selected feature remains at its noted location. I

The selected flame feature may be held at its noted location by means of the previously-listed methods of regulating. a continuous bessemer process; thatis, by regulating the input of oxygen or raw iron l8 into stream Hi. If, for example, in an acid bessemer process, the desired carbon content is, say 0.06%, and the selected flame feature is that point along stream 14 whereat the profile disappears below datum line i0, and, with the process producing the desired product when said profile disappears below datum line H] at that point along stream I l where the last of theimpinging air jets is located, then said feature may be held at said last impinging air jet by increasing or decreasing the input of oxygen into stream id, as may be required. Thus, if said feature moves upstream away from said last jet, then the carbon content of the metal product is falling below'the' desired 0.06% value, and said carbon content of the metal product may be restored to the desired 0.06% level by decreasing the input of .oxygen into stream I i until said selected-feature returns to said last impinging jet, by decreasing the input of air into said stream of metal. If, on the other hand, said selected flame feature moves downstream from said last is rising above thedesired- 0.06 value, and the "acids-6e carbon content may berestoredto the desired 0.06% value by increasing the input of air into stream I4 until said selectedfeature is returned .to said last jet.

The input of oxygen into stream H by means ofthe impinging air jets may be regulated by regulating each air jet independently, by regulating groups of said air jets together by reguif the selected feature moves upstream, said feature may be returned to the desired location by increasing the rate of input of raw iron [8 into stream l4; and if, on the other hand, the selected feature moves downstream, saidfeature may be returned to the desired location by decreasing the input of raw iron 18 into stream It.

When slag stream l2 contains iron oxide that was formed outside of the process, being added thereto in order to maintain the iron oxide content of stream l2 high and/or to increase the yield of the process, then a portion of the oxygen utilized in the process will be derived from said added iron oxide. While the process could, perhaps, be controlled in a crude sort of way by maintaining the oxygen inputvia the air jets at some constant level, while varying the iron oxide additions to slag stream l2 in order tohold the selected fiame feature at its preselected location, such a procedure would be Very sluggish in its action; however, if a powdered iron oxide is entrained in the air jets by the fluidized solids techniques, and the jets are impinging directly into or thru metal stream M, then the process may be satisfactorily controlled by controlling the amount of iron oxide being introduced as fluidized solids entrained in said air jets.

Assuming all process variables to be substantially constant, the height of the flame profile immediately above a given carbon value in stream M will be substantially constant. Accordingly, the selected flame feature may be a selected flame height that is indicative of the attainment, in stream M, of the carbon level that is a process objective. Thus, if the desired carbon level of the metal product is, say, 0.25%, then the height of the flame profile thatrepresents 0.25% carbon may be held at the point where stream It leaves trough I! to assure the production of a product containing 0.25% carbon.

While the shape of theprofile of flame between A and C is not particularly important, the profile between C and E'must conform to very definite requirements if my control method is to be firm. If the D point is being employed *as the selected feature, the angle of slope of the C--E break must be gradual enough to permit the D point to be readily observed by the human. eye; however, said slope should not be so gradual that the selected feature disappears by being spread out over too great a distance.

In tests which I made, I observed that the angle of slope of thepi-ofile of flame should be 65, the end point was approached and passed so rapidly that little accurate control could be achieved, and the-process yielded'a product that ;varied as the end point sw-ungback and forth around the selected location-this being particu- I Thus, with the -temperature on the cold side, the silicon and manganese will-tend to leave the metal well ahead of; the carbon, while .phoslarl'y true when Ia ttempted to cutiofi the process at about 025% carbon with asteep angle. ordeclin'e, for in this case 'a' comparatively-short length. of the profile represented a very large change in thejcomposition or stream M; and as I moved the profile back: and forth. around the terminalpoint in an effort to hold my selected feature at said terminal point, the metal product varied seriously in composition.for example, while aiming at 0.25% carbon in one test, two

samples of the metal product taken within one minute of each other varied from 0.19% to 0.35%

carbon. When I o'perated the process with the angle of: decline below 65, however, I had little trouble holding the carbon. content of the metal product close to. the 0125 Zfva'luev that I was aiming at. A1 thing'scon'side'r'ed, I; found that the best angle of decline was about 35, and I found that when I desired to. interrupt the process with the carbon level substantially above 0.06%',. the

more gradual the angle of. decline, the better the control; however, I founditha't when the angle of decline was less than 10' on" datum lin'e Ill, the profile of flame became quite indistinct. and ragged, with the result that I had a very difficult time controlling the process. It was assumed that the indistinct character of the profile of flame when. the angle of decline was below 10 was due to the fact that the. process had. been spread out so much. along stream 1'4; that the decarburizing reaction. no longer proceeded at a uniform ratetowards the end point, but, rather, assumed the general character of the openhearth typeof decarburizing process wherein, decarburlzation proceeds erratically'--'more specifically, the ratewo'f oxygen. input into the metal falls behind the requirements of the process, resulting in periods of process quiescence.

If my process is-being employed to control a continuous bessemer. process wherein dephosphorization is being carried out under a basic slag, my control process may be placed in operation by the previously-discussed procedure; the terminal point of the process being thatposition along stream it where the carbon content of said stream [4- has fallen to about 0.05%. Whether the attainment of this terminal point will indicate that the phosphorus has been removed also, depends upon the circumstances surrounding the operation. In general, dephosphorization will be essentially complete by the time that decarburization is essentially complete when the air jets are impinging into the basic slag and metal stream from a position thatflies above said slag stream, especially when the slag and metal streams are flowing in counter-curare impinging into-the metal stream. from aposition below the surface of said metal stream and when no particular attention is being .paid to the maintenance of a high iron oxide content in the basic slagby iron oxideadditions thereto,

--for example.

The sequence ofoxidation isalsosensitive to the temperature-ofthe flowing metal stream.

phorus will tend to leave -themetalwith the carbon if the composition of the slag favors phosphorus retentiona high V-ratio and iron oxide content. With the metal stream on the hot side, the oxidation of silicon and manganese and phosphorus will be delayed somewhat, However, whatever the oxidation sequence may be, by controlling the carbon terminal point at a preselected location along stream I4 I may control the overall process; for, in any given situation, said carbon terminal point will always bear a substantially-fixed relationship to the oxidation sequence being entertained.

. Even tho the oxygen enters the flowing metal stream in a manner that concentrates the oxidizing action in the areas which comprise the points of impingement, th elimination of the carbon is not confined to these concentrated areas of air impingement, due to the fact that the decarburizing reaction does not take place at said points of impingement, but, rather, takes place in contact with the rough hearth and sidewalls of th refining trough. This delay between action and reaction spreads out the oxidizing effect of the jets sothat the effect of each jet blends into the effect of the adjoining jets. While it might be convenient to have each jet feed the same amount of oxygen into the process, this is not essential to the success of my control process, due to the aforementioned spreading-out action of the decarburizing reaction. Furthermore, this spreading-out action tends to minimize the effect that might otherwise arise when orifices which feed air into the process become stopped-up with solidified slag and/or metal. The eifect of stopped-up orifices may be offset,

in part, by feedingsaid orifices with a common manifold wherein the air pressure rises when an orifice becomes cloggedan action that may be achieved, by feeding the air into the manifold on a constant weight basis.

While I have described the use of the flame. profile to observe the conversion of pig iron into steel, my control method may be employed in a refining process wherein apart of the decarburization is being carried out in a metallurgical vessel other than atrough as hereinbefore described. Thus, molten pig iron may be continuously introduced into an open-hearth furnace or into an electric-arc furnace, being permitted to continuously flow out of said furnace after the carbon content of the metal has been lowered to a point whereat continuous bessemerization in a refining trough will yield the declining flame profil wherein is located one of my flame features, and then, by continuously flowing said open-hearth/arc-furnace metal to a refining trough, completing the decarburization as herein described. The refining in the open-hearth/ arc furnace may be carried out in manners conventional with this type of steel making, with the view of lowering the carbon content of the metal to, say, 1.00%, before flowing said metal to the refining trough for finishing.

My control process is concerned primarily with that portion of the flame profile immediately ahead of, or upstream from, the aforementioned point whereat the decarburizing process is to be terminated; for, as has been pointed out, it is within this section of the profile that the features employable for control are to be found. The flame above the metal stream wherein the car- 'bon is still very high contributes very little to the control picture, and, accordingly, the carbon monoxide burned in forming this upstream flame is wasted, insofar ascontrol is concerned. Accordingly, I may'modify my previously-described process by providing this upstream portion of the trough with a cover.v or roof (not shown), so that only that portion of the evolved carbon monoxide which yields my selected flame feature is allowed to burn over the trough. Thus, for example, I may .cover the flowing metal stream in the region between the aforementioned A and C points, sothat the carbon monoxide evolved between said A and C points may be withdrawn from the trough without contacting the air lying thereover, so as to save said monoxide for more useful purposes, saidmonoxide being withdrawn from the covered troughvvia suitable ducts (not shown). Then, by allowing the monoxide evolved between C and E to burn freely over the uncovered portion of the trough, I may control the process. Obviously, if the air jets in the covered portion of the trough are impinging into the metal stream from a position located above said stream, a portion of the evolved monoxide will be burned in reaction with said jets.

The previously-described features of the profile of flame which may be employed to control a continuous bessemer process are all of the type that must ordinarily be observed by the human eye. As mentioned. previously, the flame height may be employed as the selected feature, for the height of the flame over a given portion of the decarburizing process is related to the progress of said decarburizing process. By viewing a portion or section of the profile thru a viewing slit 2% in the region where the profile is rapidly declining as the process approaches the terminal point, by means of an electric eye that is connected to measuring means, movements of the flame profile upstream or downstream may be electrically detected and followed; for, as in the figure, when said profile moves downstream, the amount of light passing thru slit 20 increases, and when said profile moves upstream, the amount of light passing thru slit 2%] decreases. Slit in order to be fully responsive to profile movements, should be oriented with respect to the angle of decline so that profile movements are reflected by large changes in the amount of light passing thru slit 2E. The amount of light passing thru slit 20 may be measured and/or recorded by conventional methods and means;

that is, by a photoelectric cell that is connected to a suitable meter for measuring/recording the current that is generated/passed by said cell when said light passes thereinto. A further refinement involves the connection of electronic measuring means to control equipment, so that profile movements, detected and measured by an electric-eye measuring means, are immediately and automatically ofiset as said electronic measuring means actuates a control mechanism that adjusts the input of air into the refining process, said adjustment being in accordance with the degree that the process has departed from normal. It will be'realized, accordingly, that that portion of the flame profile which is viewed thru slit 28 is but another flame feature that may be employed to control the continuous bessemer according to my method.

Still another flame feature that may be employed is the temperature attained by the gas at some selected distance above the profile, and this temperature feature may be employed to automatically control the position of the profile over the trough in the manner just mentioned in connection with slit iii. For example, one or more thermocouple(s) may be positioned over the profile of flame and over the position whereat it is desired to terminate the decarburizing process, said thermocouple(s) being positioned above and, say, one foot away from the flame, said thermocouple(s) being connected to suitable measuring, recording and/or recording equipment. When, now, the profile of flame moves downstream, it approaches closer to said thermocouple, resulting in an immediate reaction on the part of the control equipment connected to said thermocouple-in this case, said control equipment will increase the oxygen input into the process until the profile of flame moves back to the position describable as the neutral point, and if, on the other hand, the profile of flame moves upstream away from said thermocouple, said thermocouple will record a lower temperature, and so act to actuate the connected control mechanism so as to decrease the input of oxygen until said profile returns to the desired position.

The molten metal being bessemerized will always contain carbon; however, said molten metal may or may not contain other oxidizable impurities. Accordingly, I refer in my claims to the molten raw iron whose refinement is to be controlled by my profile method of control as: molten high-carbon iron, and I refer to the product of the process controlled by my method as: molten low-carbon iron.

There are two basic reactants involved in my control process, namely, oxygen and molten iron containing carbon. The expression oxygen is employed in my claims to denote said reagent: oxygen. As mentioned previously, the continuous bessemer process may utilize oxygen derived from a number of sources; for example, the process may utilize the oxygen being introduced into the slag and/ or metal thru the instrumentality of the impinging air jets, or said process may utilize the oxygen content of iron oxide being fed into said slag and/or metal, or said process may utilize the oxygen content of the molten slag stream in contact with which the metal stream flows, or the process may employ a combination of these oxygen sources at difierent, or the same, time.

Having now described several forms of my invention, I wish it to be understood that my invention is not to be limited to the specific form or arrangement of steps hereinbefore shown and described, or except insofar as such limitations are specified in the appended claims.

I claim as my invention:

1. In a continuous bessemer process wherein flame appears above and along a trough within which a stream of high-carbon iron is decarburized with the aid of a series of air jets, the method of controlling said decarburizing process, which comprises: introducing oxygen into the stream of molten metal within said trough so that the profile of the flame above the concluding portion of said decarburizing process declines as the carbon content of said metal stream declines, the angle of said decline being within the range between 10 and from the surface of said stream of molten metal; and selectively increasing or decreasing the input of oxygen into said decarburizing process so that a discernible feature of said flame profile within said decline is maintained at a substantially-fixed position along the stream of molten metal within said trough.

2. The method according to claim 1 in which said discernible flame feature is the height of the profile of said flame above said position along said stream of molten metal within said trough.

3. The method according to claim 2 in which said flame height is measured by viewing a portion of said flame profile by means of a photoelectric cell positioned to view said flame profile at said position along said stream of molten metal within said trough.

4. The method according to claim 2 in which said flame height is measured by means of a thermocouple that is positioned above and normally out of direct contact with said flame at said position along said stream of molten metal within said trough.

5. The method according to claim 1 in which said discernible flame feature is the position along said trough where the profile of said flame essentially disappears below the top of said trough.

6. The method according to claim 1 in which said discernible flame feature is an arrest in the rate of decline of the profile of said flame as said process approaches its conclusion.

7. The method according to claim 1 in which carbon monoxide arising from said decarburizing prior to said concluding portion of said decarburizing process is withdrawn from said trough without being permitted to burn over said trough.

JAMES FERNANDO JORDAN.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES The Acid Bessemer Process of 1940, by H. W. Graham, and Photocell Control for Bessemer Steel Making, by H. K. Work. Published in volume 145, pages 112 to 150, of Transactions of the American Institute of Mining and Metallurgical Engineers. 

1. IN A CONTINUOUS BESSEMER PROCESS WHEREIN FLAME APPEARS ABOVE AND ALONG A TROUGH WITHIN WHICH A STREAM OF HIGH-CARBON IRON IS DECARBURIZED WITH THE AID OF A SERIES OF AIR JETS, THE METHOD OF CONTROLLING SAID DECARBURIZING PROCESS, WHICH COMPRISES: INTRODUCING OXYGEN INTO THE STREAM OF MOLTEN METAL WITHIN SAID TROUGH SO THAT THE PROFILE OF TE FLAME ABOVE THE CONCLUDING PORTION OF SAID DECARBURIZING PROCESS DECLINES AS THE CARBON CONTENT OF SAID METAL STREAM DECLINES, THE ANGLE OF SAID DECLINE BEING WITHIN THE RANGE BETWEEN 10* AND 65* FROM THE SURFACE OF SAID STREAM OF MOLTEN METAL; AND SELECTIVELY INCREASING OR DECREASING THE INPUT OF OXYGEN INTO SAID DECARBURIZING PROCESS SO THAT A DISCERNIBLE FEATURE OF SAID FLAME PROFILE WITHIN SAID DECLINE IS MAINTAINED AT A SUBSTANTIALLY-FIXED POSITION ALONG THE STREAM OF MOLTEN METAL WITHIN SAID TROUGH. 